@guardbee/mcp-dns-intelligence

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An MCP server that enumerates DNS records, detects SPF / DMARC / DKIM misconfigurations, and finds dangling subdomains. Uses Node.js's built-in dns/promises — no external dependencies.

This package sends usage telemetry by default (tool name + short parameters — see @guardbee/mcp-telemetry). Disable with GUARDBEE_TELEMETRY=0.

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Features

• Full DNS Enumeration — A, AAAA, MX, NS, TXT, CNAME, SOA records
• SPF Analysis — +all, ?all, excessive DNS lookups, duplicate record detection
• DMARC Analysis — policy (none/quarantine/reject), pct, missing rua address
• DKIM Check — probes 9 common selectors (default, google, selector1, mail, etc.)
• Subdomain Enumeration — 60+ common subdomains; dangling CNAME detection (14 cloud providers)
• Email Security Summary — combined SPF + DMARC + DKIM analysis with copy-pasteable fix recommendations
• 23 Unit Tests — pure logic tests, no network connection required

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Quick Start

npm install -g @guardbee/mcp-dns-intelligence

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "guardbee-dns-intelligence": {
      "command": "npx",
      "args": ["-y", "@guardbee/mcp-dns-intelligence"]
    }
  }
}

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MCP Tools

Tool	Description
enumerate_dns	Enumerates all DNS records for a domain and runs SPF/DMARC/DKIM analysis
enumerate_subdomains	Probes common subdomains; flags dangling CNAMEs
check_email_security	Combined SPF + DMARC + DKIM audit with fix recommendations
lookup_dns	Targeted DNS lookup for a specific record type (A/MX/TXT/etc.)

Example Usage

You can ask Claude:

"Is there a problem with example.com's DNS configuration?"

"Audit example.com's email security — SPF, DMARC, and DKIM"

"List example.com's subdomains, flag any dangling ones"

"What are example.com's MX records?"

Example Output

Email Security Check: example.com
──────────────────────────────────────────────────

── SPF ─────────────────────────────────────────
✓ v=spf1 include:_spf.google.com -all

── DMARC ───────────────────────────────────────
✗ No DMARC record found at _dmarc.example.com
  Add:  v=DMARC1; p=quarantine; rua=mailto:[email protected]

── DKIM ────────────────────────────────────────
✓ Found DKIM selectors: google

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SPF Findings

Code	Severity	Description
SPF_MISSING	🟡 Medium	No SPF record found
SPF_PERMISSIVE_ALL	🔴 Critical	+all — allows any server
SPF_NEUTRAL_ALL	🟠 High	?all — doesn't reject unauthorized senders
SPF_NO_ALL	🟡 Medium	No all mechanism
SPF_TOO_MANY_LOOKUPS	🟠 High	> 10 DNS lookups — causes SPF to fail
SPF_DUPLICATE	🟠 High	Multiple SPF records

DMARC Findings

Code	Severity	Description
DMARC_MISSING	🟠 High	No DMARC record
DMARC_NO_POLICY	🟠 High	Missing p= policy
DMARC_POLICY_NONE	🟡 Medium	p=none — monitoring mode, no enforcement
DMARC_PCT_LOW	🔵 Low	pct < 100 — partial enforcement
DMARC_NO_RUA	🔵 Low	No aggregate report address (rua)

Dangling Subdomain Detection

Subdomains whose CNAME points to one of the following providers but doesn't resolve are flagged as dangling and carry a subdomain-takeover risk:

AWS S3, Azure App Service, GitHub Pages, Heroku, Netlify, Vercel, Cloudflare Pages, Surge, Pantheon, WP Engine, Ghost, Shopify, Fastly, AWS CloudFront

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CLI — CI/CD Integration

In addition to MCP server mode, this can also be used directly as a CLI:

# Full DNS + email security check
npx @guardbee/mcp-dns-intelligence check example.com

# Fail only on high and above
npx @guardbee/mcp-dns-intelligence check example.com --fail-on=high

# Subdomain scan — exits 1 if a dangling CNAME is found
npx @guardbee/mcp-dns-intelligence subdomains example.com

# Subdomain scan with higher concurrency
npx @guardbee/mcp-dns-intelligence subdomains example.com --concurrency=50

# JSON output
npx @guardbee/mcp-dns-intelligence check example.com --format=json

Exit codes: 0 = no issues · 1 = findings above threshold / dangling subdomain · 2 = error

Configuration via guardbee.yml

Create a guardbee.yml at your project root to persist CLI flags. CLI flags always override file settings.

dns-intelligence:
  fail-on: high          # critical | high | medium | low
  concurrency: 20        # parallel subdomain probes
  domains:               # used when no domain is given on the CLI
    - example.com
    - staging.example.com

See guardbee.example.yml for a sample file.

GitHub Actions — DNS Security Audit

name: DNS Security Check
on:
  schedule:
    - cron: "0 6 * * *"  # Every day at 06:00
  workflow_dispatch:

jobs:
  dns-check:
    runs-on: ubuntu-latest
    steps:
      - name: Check DNS configuration
        run: npx @guardbee/mcp-dns-intelligence check ${{ vars.DOMAIN }} --fail-on=high

      - name: Scan for dangling subdomains
        run: npx @guardbee/mcp-dns-intelligence subdomains ${{ vars.DOMAIN }}

GitLab CI

dns-security:
  image: node:20
  script:
    - npx @guardbee/mcp-dns-intelligence check $DOMAIN --fail-on=high
    - npx @guardbee/mcp-dns-intelligence subdomains $DOMAIN
  only:
    - schedules

Pre-Deployment Email Security Check

- name: Verify email security records
  run: |
    npx @guardbee/mcp-dns-intelligence check ${{ vars.DOMAIN }} \
      --fail-on=high \
      --format=json | tee dns-report.json

- name: Upload DNS report
  uses: actions/upload-artifact@v4
  with:
    name: dns-security-report
    path: dns-report.json

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Development

npm install
npm test          # 23 unit tests
npm run build     # TypeScript compile

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License

MIT — GuardBee